Photophysical features

Pyrene shown a number of photophysical features that made it an attractive fluorophore to probe the microenvironment in micellar aggregates [19]. For the peaks of pyrene PL, two important peaks at about 373 nm and 390 nm among the five dominant peaks of pyrene fluorescence were numbered as 1 and III, respectively [20]. It has been known that intensity ratio of peak 111 to I (III/I) increased as the polarity at the solubilization site of pyrene decreases. Figure 6 shows fluorescence spectra (A.ex = 310 nm) of pyrene in precursor gel containing TPA and I-IV samples denoted as (a), (b), (c), (d) and (e), respectively. The value of 111/1 of pyrene does not change under silicalite-1 gel due to no formation of micelle. However, in the Fig. 6d (sample II), III/I ratio is rapidly increased, while sample III and IV are decreased slightly again. Previously, Park et al. have reported that 111/1 ratio of pyrene for... 

The polymer materials not only act as supports for the dye and other necessary additives in the sensing phase, providing protective covering for the transduction element polymers also play various roles in chemical sensors. They provide a compatible environment for the indicator molecules, maintaining or improving the appropriate photophysical features (compared to those observed in homogeneous solution) on which the sensing principle is based. In many cases they collect and concentrate the analyte molecules on sensor surfaces. In addition, the polymer can play an important role in the sensitivity and selectivity of an optical sensor, and its interactions with indicator and analyte molecules influence the analytical performance of the device. 

Owing to the intrinsic optical and photophysical features discussed for metallopolyynes, it is expected that they have great potential as active materials in optical and photonic devices. Over the years, numerous studies have shown that these metallopolymers can be exploited for a collection of electronic and optoelectronic applications. 

An excellent short review of C-H bond activation including both thermal and photochemical mechanisms has been provided by Labinger and Bercaw. Lees has reviewed the photochemical and photophysical features of these reactions. Bergman has described the contributions of his group toward the understanding of the mechanisms of C-H activation up to 1992, and within the context of physical organic chemical methods. Schneider has examined the similarities between Si-H and C-H activation. Shilov and ShuFpin have provided extensive reviews of C-H activation. As with Si-H oxidative addition, the spin state of the photochemical intermediate plays a major role in the probability of insertion. This has been reviewed for the specific case of methane activation. 

A two-component system containing both the photosensitizer and the electron relay has been obtained by covalently linking a cobalt-cage subunit to an anthracene moiety. An. The system 27 is not fluorescent ( < 2 x 10 ), owing to the occurrence of an intramolecular quenching of the excited anthracene by the Co complex. Investigations on the photophysical features of 27 (i.e., transient absorp-... 

Isomerism, optical activity and liquid crystalline materials exhibit intersting photophysical features where luminescence is often a valuable probe. Fluorescence analysis of thermotropic biphenyl liquid crystalline polyesters has shown a... 

Chapter 2 PHOTOCHEMICAL TECHNIQUES TO UNDERSTAND PIWTOCHEMICAL AND PHOTOPHYSICAL FEATURES ON SOLID SURFACES... 

Thanks to their unique architecture, chirahty, supramolecular properties, and photophysical features, thiahelicenes are surely among the most versatile poly-conjugated systems for which a huge number of appHcations have been envisaged and investigated. In many cases these explorations have... 

The building block of BODIPY can be well tailored by structural modification, enriching the family of BODIPY dyes. Indeed, the BODIPY scaffold serves as a promising platform for the construction of molecular sensors. Given that BODIPY derivatives bear excellent characteristics, such as intense fluorescence quantum yields, sharp absorption and fluorescence emission spectra, a tremendous expansion has been witnessed in BODIPY-based probes for versatile applications. The established BODIPY-based probes always exhibit fluorescence turn-on or ratiometric responses to a target, by making full use of photophysical processes with common channels such as PET, ICT or FRET. There is no doubt that the rational construction of BODIPYs with these photophysical features still serves as effective strategies to further develop powerful probes or chemodosimeters. 

The DBH derivative 3a constitutes the first case for which direct spectroscopic characterization of the long-lived (0.63 is) triplet state was achieved, in view of the efficient singlet-to-triplet intersystem crossing ca. 0.5). This unprecedented finding stimulated further studies on the azoalkanes 3 through 9 in an effort to define the essential structural requirements for the exceptional photophysical features of azoalkane 3a.This work reports, for the first time, the phosphorescence emission spectra of azoalkanes (3, 4a, 6a, 8, and para-substituted [p-F and p-Br] derivatives 3c] at 77K. As representative cases, the photophysical properties of azoalkanes 3a and 4a are compared in Table 93.1 with those of... 

---